Furnace-opening seal



Patented Aug. 20, 1929.

UNITED STATES PATENT OFFICE- ORA A. COLBY, OF MANSFIELD, OHIO, ASSIGNORTO WESTINGHOUSE ELECTRIC & KAN- UFACTURING COMPANY, A CORPORATION OFPENNSYLVANIA.

FURNACE-OPENING SEAL.

Application filed January 19, 1928. Serial No. 247,893.

My invention relates to furnaces and more particularly to furnaces ofthe tunnel type having open ends to permit the continuous movement ofmaterial undergoing heat-treatment through the same.

In furnaces of the above type, difficulty hasbeen experienced inpreventing the loss of heat through their open ends, and, since the endsmust be maintained open to'permitthe passage of material therethrough,the expedients usually resorted to, such as doors or bafiles, have beenfound to be undesirable and ineffective.

It is an object of my invention, therefore, to provide means, infurnaces of the above mentioned type, for minimizing the loss of heatthrough the open ends thereof and, at the same time, permitting the freemovement therethrough of work to be heated.

I'have found, by experiment, that, in a furnace of the tunnel type,there is a definite circulation of air through the heating chamber whichresults in a considerable loss through the chamber by a plurality ofhooks of heat, by convection, through the open ends thereof. Streams ofcold air enter the chamber, and streams of heated air leave the chamber,through the open ends thereof. I have found, byexperiment, thatthere isa horizontal line, at approximately two thirdsof the height of the areaof the open end, below which the cold air enters, and above which theheated air leaves, the furnace chamber. v

The actual loss of heat through the ends of the chamber depends largely,of course, upon the dimensions of the chamber and the workingtemperature employed. By experiment, I have found that, in anelectrically heated furnace chamber approximately 125 feet in length andoperating at a temperature of 1650 F., the heated air leaving thechamber moves at approximately 300 feet per minute and represents a lossof about 100 kw. of electrical energy.

In practicing my invention, I provide, in conjunction with anelongated'furnace chamber having open ends, means for forcing aplu'ralit of streams of air, at high pressure, across t e open ends insuch manner that the direction of movement of the stream of heated airtherethrough is altered and interrupts the incoming stream of cold air.

In the drawing, Figure 1 is a view, in vertlcal longitudiableheat-insulating refractory material defining an elongated furnacechamber 2. Thestructure is suitably reinforced by channel andangle irons4 which extend a short distance above the roof of the furnace to supporta conveyor, as hereinafter described.

A longitudinally extending slot 6 is provided in the roof of the furnaceand is coextensive, in length, with the length of the furnace chamber.

Materialto be heat-treated is conveyed 8 which extend through the slot 6and have secured, at the upper extremities thereof,

rollers 10 or other suitable antifriction means; The rollers 10 aresupported upon a-trackway .12, secured to the horizontally extendingportions of the reinforcin structure 4, and are adapted to be movetherealong. The hooks are connected above the level of the furnace roof,by a plurality of links-14, constitutin a continuous conveyor chain,whereby the ooks may be moved in .unison through the chamber. Theconveyor chain extends somewhat beyond the ends of the furnace and issuitably connected to a drivin means to eiect the movement thereof. T edriving means and the return path for the conveyor chain have beenomltted from. the drawing, for the sake of clearness, but, sincethe'conveyor shown is of a type well known in the art, furtherillustration thereof is not deemed necessary.

The furnace chambe r is heated by suitable the furnace ad'acent andarallel to the upper e of t eopen en thereof and are operativelyassociated with an air compressor (not shown) or other suitable sourceof high-pressure air. A slot is provided in the horizontally extendingportions of the conduits, longitudinally thereof, and 'is adapted toreceive a block 20, which is apertured, as at 22, to constitute aplurality of nozzles. The free ends of the conduits 18 are closed, andthe blocks are fitted tightly in the slots formed in the conduits, sothat, Wlth the conduits connected to a source of high-pressure air, aplurality of streams of air are forced, at high velocity, across thefurnace opening. The number of jets employed may bevaried at will, butthere should be such number that the streams of air formed thereby areclose enough to constitute, in effect, an air curtain across the furnaceopening.

In "the modification shown in Fig. 3,-one of the conduits 18 isextended, as at 24, to lie along the slot 6 in the furnace roof. Nozzlesare also provided in the extended portion, and streams of air aredirected thereby across the slot to prevent the loss of heattherethrough.

As above pointed out, in the normal operation of the furnace, a streamof heated air, at relatively high velocity, flows through the upperportion of the open ends of the furnace, and .a stream of cold airenters through the lower portion. The curtain of air movin at highvelocity from the nozzles 22 alters t e normal circulation of coldandheated air, however, and-prevents the flow of heated air from thefurnace chamber. The velocity of the air from the nozzles is of such avalue that the stream of heated air is bent downwardly into the path ofthe cold incoming air, whereby the velocity of the conveyor slot 6.

Throughout the specification, air has been Y referred'to as the mediumvconstituting the furnace chamber atmosphere, and that employed in theconduits 18. Obviously, however, myinvention is applicableto furnacesirrespective of the chemical characteristics of the furnace chamberatmosphere, and any desired fluid may be employed in the conduits 18.

By my invention, I have provided a simple and effective means forpreventing the loss of heat from an open-end furnace chamber, which doesnot interfere with the passage of work through the ends of the furnace,and which increases, to a marked degree, the operating efficiency of thefurnace. The moving fluid constitutes a permeable screen or door forreducing the amount of outgoing heated air and the incoming cool airwhile permitting the free movement of articles through the furnace.

Various modifications may be made in the device embodying my inventionwithout departing from the spirit and scope thereof, and I desire,therefore, that only such limitation shall be placed thereon -as areimposed by the prior art and set forth in the appended claims.

I claim as my invention;

1. In a heat-treating furnace, the combination with an elongated heatingchamber open at the ends thereof and having a normal efllux of heatedairthrough said open ends adjacent to the roof of the chamber and an influxof cold airthrough the lower portion of said open ends, of meanscomprising perforated conduits located above theends for forcing air, athigh velocity, downwardly across said ends to prevent said efllux ofheated air and to force said heated air into the path of said stream ofcold air.

2. A heat treating furnace comprising a plurality of walls including aroof and defining an elongated heating chamber open at both ends and alongitudinally-extending slot in said roof, in combination with meansfor moving material to be heat treated through said chamber, said meanshaving depending portions to move through said slot, and conduitportionslocated closely adjacent to the ends of the roofand each extendingbetween a side wall and the slot, a plurality of spaced nozzles in thebottom of each conduit and means for forcing air at high velocitythrough said conduits and said nozzles to provide air curtains acrosssaid open ends.

In testimony whereof, I have hereunto subscribed my name this 12 day ofJanuary,

- .oRA A. COLBY.

